Reviewing past environments in a historic house using building simulation

This paper reviews different heatingregimes applied to the same space,using building simulation. Theconstruction of a computer simulationmodel to investigate past and presentenvironments in a historic house libraryis described. The model simulated fourhypothetical scenarios, based on realdata. The simulation outputs werereviewed in terms of the risk ofphysical and chemical deterioration,and their relationship with an existingnational standard for archives. Thepossibility of simulating pastenvironments to investigate naturalageing is also discussed

Condensation risk: comparison of steady-state and transient methods

Accurate assessment of both surface and interstitial condensation risk is important not only to reduce the damaging effect of moisture within the structure of buildings, but also to provide a healthy environment free from mould growth. The current British Standard (BS EN ISO 13788: 2002) contains an assessment procedure based on the assumption of a steady-state heat flow through the building envelope, neglecting the transient nature of the problem. This paper compares and evaluates numerical results of the condensation risk calculation under both steady-state and transient conditions using the existing numerical codes. Significant differences are apparent between the predictions of the simple (steady-state) and complex (transient) methods for all construction details modelled

Population inversion in optically pumped asymmetric quantum well terahertz lasers

Intersubband carrier lifetimes and population ratios are calculated for three- and four-level optically pumped terahertz laser structures. Laser operation is based on intersubband transitions between the conduction band states of asymmetric GaAs-Ga(1 – x)Al(x)As quantum wells. It is shown that the carrier lifetimes in three-level systems fulfill the necessary conditions for stimulated emission only at temperatures below 200 K. The addition of a fourth level, however, enables fast depopulation of the lower laser level by resonant longitudinal optical phonon emission and thus offers potential for room temperature laser operation. © 1997 American Institute of Physics

An evaluation of the hygrothermal performance of 'standard' and 'as built' construction details using steadystate and transient modelling

Accurate assessment of both surface and interstitial condensation risk at the design stage of buildings is of great importance - not just to minimise the damaging effects moisture can cause to building envelopes, but also to contribute to the provision of adequate indoor air quality. Guidance certainly does exist with regards to limiting thermal bridging in order to prevent condensation occurring on new constructions. However, a recent study has provided clear evidence that the reality, both in translating the available guidance into a specific design and in construction on site is often rather different from the 'ideal'. This paper reports on that study and compares and evaluates the hygrothermal performance of construction details for different phases during the building life cycle. The results of both the surface and interstitial condensation risk simulations under both steady-state and transient conditions are presented and discussed. Significant differences in the hygrothermal performance of 'standard' and 'as built' construction details are observed

Condensation risk – impact of improvements to Part L and robust details on Part C Final report: BD2414

This report summarises the main findings of the project ‘Impacts of Improvements to Part L and Robust Construction Details (RCD) on Part C’. The work consisted of a fieldwork element, undertaken by Leeds Metropolitan University and a modelling element carried out by University College London. Details of the work programme are contained in Appendix 1. The fieldwork consisted of the analysis of design material and site surveys from 16 housing developments constructed to Part L 2002 and adopting the Robust Construction Detail route to compliance. The modelling element of the project sought to identify the extent to which the ‘as built’ details give rise to a significantly increased condensation risk as compared to the relevant ‘standard’ robust construction details, as defined in the guidance. In addition to assessing ‘as built’ performance, the modelling phase of the project has investigated the suitability of the relevant calculation methods used to assess the risk of surface and interstitial condensation and mould growth. This report draws together the important conclusions from the project which has previously been presented in several very detailed interim reports and also for the first time presents the results of a workshop where these results were discussed to obtain industry feedback. The overall conclusions, future work and dissemination plans are also presented

Contradictions in social enterprise: do they draw in straight lines or circles?

This paper provides a critical perspective on the discourse surrounding the concept of social enterprise. The paper shifts the lens away from numbers to consider how actors see themselves as social enterprises. The authors make sense of the foundations upon which the concept of social enterprise and entrepreneurship is ‘drawn’ – quite literally – by considering linear models and diagrams that analyse social enterprise on a continuum between non-profit (mission) and profit (market) orientation. A great deal has been made of the success and growth of social enterprise. The imagery in the literature reflects an emphasis on growth resulting from ‘the rising tide of commercialisation of non-profit organisations’ (Dees, 1998) with the result that the CBI now includes over 50,000 organisations in a social enterprise sector (SBS, 2005). Despite reports of rapid growth, there is awareness that ‘take-up of social enterprise model … is patchy and fails to reflect the enthusiasm with which it is discussed’ (Stevenson in Westall &amp; Chalkley 2007). We ask why? A methodological approach involving visual drawings by actors reveals stories and sensemaking experiences of social enterprises. Open conversations enabled the researchers to gain deep insights that would not have been as insightful through a quantitative approach. The key findings suggest: Firstly, participants report tensions when pursuing social and economic goals simultaneously. Secondly, whilst some welcome opportunities that are emerging, others perceive substantive threats to the third sector. Thirdly, Social enterprise emerges as a diverse and heterogeneous movement located at the boundaries of public, private and voluntary sectors. At each boundary, different constitutional forms and practices are seen. In conclusion, it is argued that the linear perspective itself gives the impression that there is a ‘patchy’ take up of social enterprise. A heterogeneous perspective reveals that theory and policy development is patchy, rather than social enterprise practices. The unique contribution this research paper offers is within the depth of enquiry and insight into the actual practices provided from those within the field. The critical perspective is taken from the literature and discussed in the settings of the actors in the field which provides practitioners, business support agencies and academics with a different level of empirical investigation that captures an originality and narrative that has barely been explored before.</p

The effect of transition hysteresis width in thermochromic glazing systems

Thermochromic glazing theoretically has the potential to lead to a large reduction in energy demand in modern buildings by allowing the transmission of visible light for day lighting whilst reducing unwanted solar gain during the cooling season, but allowing useful solar gain in the heating season. In this study building simulation is used to examine the effect of the thermochromic transition hysteresis width on the energy demand characteristics of a model system in a variety of climates. The results are also compared against current industry standard glazing products. The results suggest that in a warm climate with a low transition temperature and hysteresis width energy demand can be reduced by up to 54% compared to standard double glazing

Variation of Thermochromic Glazing Systems Transition Temperature, Hysteresis Gradient and Width Effect on Energy Efficiency

Due to increasing pressure to reduce the energy demand in buildings, thermochromic thin film based glazing has become a recognized potential solution due to the intrinsic ability to modulate the solar heat gain of a window as a function of the materials temperature. These “intelligent” glazings have been investigated for several years, and it has been found that, through variation of synthetic route, the thermochromic properties (transition temperature, hysteresis gradient and width) can be altered; however, less attention has been applied to how such alterations affect the overall energy savings attributed to the materials. In this study the building simulation software EnergyPlus TM has been used to model a series of idealized thermochromic spectra in a series of different environments to evaluate their energy saving potential against both clear glass systems and industry standards. The idealized spectra are used to see what effect each of the materials thermochromic properties and therefore elucidate which are the most important with respect to the energy saving properties. It was found that the best thermochromic materials were those with a narrow sharp hysteresis and a low transition temperature and result in an increase in energy saving between 30%–45% across the different environments compared to clear glass systems